Selective blanking of video display

ABSTRACT

Alpha numeric information supplied in the form of electrical signals from a plurality of input sources can be fed to a central control unit and rearranged therein for subsequent transmission to one or more video display monitors, each monitor employing a separate cathode-ray tube. Each source can be assigned a preselected portion of the display area on each tube whereby each tube can display the information from each of the sources in its preassigned areas in the form of a complete display of all of the sources apparently simultaneously. Our invention is adapted for use in systems as described above. It employs circuitry located partially in the common unit and partially in each monitor for the selective blanking of one or more display areas in one or more tubes. In other woeds, information from some of the sources may be displayed by any one monitor while at the same time information from others of the sources can be blanked out on the same monitor. To this end, control pulses identified with corresponding input sources are sequentially introduced at the unit for transmission to all of the monitors. Circuitry at each monitor can be selectively enabled to detect such control pulses and to utilize the detected pulses for selective blanking.

United States Patent lnventors Frederic D. Rando PrimaryExaminer-Stanley D. Miller, Jr.

Cherry Assistant Examiner-R. E. Hart y'illliarn P. Rogers, Collingswood,both of An0rneysNorman .l. OMalley and Theodore C. Jay, Jr. [21] Appl.No. 756,916 [22] Filed Sept. 3, 1968 ABSTRACT: Alpha numeric informationsupplied in the form [45] Patented Nov. 30, 1971 of electrical signalsfrom a plurality of input sources can be fed [73] Assignee UItronic Syte Corporation to a central control unit and rearranged therein forsubsequent transmission to one or more video display monitors, eachmonitor employing a separate cathode-ray tube. Each source [54]SELECTIVE BLANKING OF VIDEO DISPLAY can be assigned a preselectedportion of the display area on 6 Claims, 5 Drawing 8 each tube wherebyeach tube can display the information from [52] [1.8. CI 328/14 each ofthe sources in its preassigned areas in the f of a 178/75 328/94 307/2,307/208 complete display of all of the sources apparently simultane- 511mu ...ll03b 19/00 50 Field of Search 340 3241 l f use l l as descrbed178/75 E 75 DC,69 5 TV; fl/247318 above. It employs circuitry locatedpartially in the common 234 236, 268 328/l4 I87 unit and partially ineach monitor for the selective blanking of one or more display areas inone or more tubes. In other [56] Refe Ci d woeds, information from someof the sources may be dis- UNITED STATES PATENTS played by any onemonitor while at the same time information 3 013 H6 12",) Sziklaiet al178/7 5 C from others of the sources can be blanked out on the same3:047'737 7/l962 Kolodin monitor. To this end, control pulses identifiedwith cor- 3.437'873 I969 gg 340/324 1 responding input sources aresequent ally introduced at the 3 9'2 I969 /32 'l unit for transmissionto all of the monitors. Circuitry at each monitor can be selectivelyenabled to detect such control pulses and to utilize the detected pulsesfor selective blanking.

/0 S/IVGLE 5 HOT MULT/ V18 RR 70/? COUNTER PULfiES 4O a 0 a4- BLANK/N6 JPu; 555 re FLOP T/M/NG O M lol/ S55 44 CLOCK PULSfiS 0 SELECTIVEBLANKING OF VIDEO DISPLAY BACKGROUND OF THE INVENTION US. Pat.application Ser. No. 657,664, filed Aug. 1, 1967 and assigned to theassignee of the present application, discloses a system for receivingelectrical signals from three sources, i.e., the New York StockExchange, the American Stock Exchange and a News Service. The first twosources supply transactions information, while the last-named sourcesupplied financial news.

A central control unit receives these signals, arranges same in propertime sequence for sequential display, generates synchronization pulsesand transmits the pulses and signals, properly interleaved, to aplurality of monitors for selective display.

A typical full display at a monitor presents transactions of the NewYork Stock Exchange on a top portion of the cathode ray tube; AmericanStock Exchange transactions on the midportion of the tube; and financialnews information on the remaining lower portion of the tube.

The monitors are leased rather than purchased by the end user, who ischarged a fee for each source that is to be displayed. When an end userwishes to pay for only one, or possibly two, of the sources and does notwant to pay for the other source or sources, it is necessary to blankout the unwanted sources in the display on his monitor. Sinceinformation from all sources is fed to all monitors for display, it isnecessary to provide means for separately and selectively blanking eachmonitor.

SUMMARY OF THE INVENTION In our invention, separate control impulsesgenerated in the control unit are introduced into the video stream priorto transmission. The timing of the impulses is such that an impulseprecedes transmission of source information. Thus, one impulse precedesNew York Stock Exchange data, a second impulse precedes American StockExchange data and a third impulse precedes News Service data.

Each impulse must be so timed as to avoid creation of intersymbolinterference. To this end, each impulse can be superimposed upon thesynchronization pulses initiating the display of the correspondencesource at the monitor. Each monitor is provided with equipment fordetecting the presence of the control impulses. This equipment can bemanually adjusted to respond to any one or more of these pulses or torespond to none. In the latter case, the monitor displays all sources.In the former case, the impulses are detected and can be used thereafterto blank out the appropriate portions of the display, for example, by agate to interrupt the flow of video signals in the monitor for aselected interval or intervals. If desired, the detected impulses can beused for other control purposes in addition to or instead of blanking.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a block diagram of circuitry used in our invention asinstalled in a central control unit;

FIG. 2 illustrates wave forms used in the circuitry of Fig. I;

FIG. 3 is a block diagram of circuitry used in our invention asinstalled in a monitor; and

FIG. 4a and 4b illustrate wave forms used in the circuitry of Fig. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS convert high inputs to lowoutputs and vice versa. For ease of illustration, conventional groundconnections have not been shown in the drawings.

The system described in the US. Pat. application SN. 657,664 referred toabove employs television-receiver monitors of conventional type using a60 hertz field frequency with a 260-line field. The horizontal andvertical synchronizing signals conform to United States standards forthis field frequency and number of field lines.

Referring now to figures 1-4, the output of a single shot multivibrator10 is connected to the first input 12 of a gate 14 and is also connectedto a first input 18 of another gate 20. The output of gate 20 isconnected to input 24 of flip-flop 26. The output of flip-flop 26 isconnected to a second input 16 of gate 14. Counter pulses 40 aresupplied to the input of the multivibrator. Control or blanking pulses42 are supplied to a second input 22 of gate 20. Timing pulses 44 aresupplied to input 28 of the flip-flop, while clock pulses 50 aresupplied to an input 30 of the flip-flop. All input pulses areunidirectional and have positive polarity.

The counter pulses are produced at horizontal line scan rate by acounter (not shown). Multivibrator 10, upon the reception of a counterpulse 40, produces a single positive going rectangular pulse 46 which isa conventional horizontal line scan pulse. When pulse 46 arrives atinput 12 of gate 14 and, at the same time, the output of flip-flop 26 ishigh, a rectangular pulse 48 unaltered in wave form, but reversed inpolarity, passes through gate 14.

However, when a control pulse 42 and a timing pulse 44 are presentsimultaneously at the inputs of the flip-flop, the flipflop output isswitched from high to low for the duration of the timing pulse 44 and isthen switched from low to high by the clock pulses 50 which are used tomaintain the flip-flop output high. Note that timing pulses 44 arealways produced during intervals between clock pulses.

When the flip-flop output is switched from high to low and back again,thus producing a flip-flop output impulse 52, at the time that therectangular pulse 48 from the multivibrator is passing through gate 14,the impulse 52 is superimposed upon a portion of the rectangular pulse,thus producing a composite pulse 54 appearing at the output of gate 14.

As a result, each time a counter pulse is supplied to the multivibrator,a pulse is produced at the output of gate I4. This pulse is either pulse48 or pulse 54. In either event, this pulse is supplied to one or moremonitors as a horizontal synchronizing pulse. The presence of impulse 52can be detected by circuitry at the monitor for use in selectiveblanking of portions of the display. When the horizontal synchronizingpulse has only the rectangular shape, circuitry at the monitor does notfunction and no selective blanking can occur. The control pulses 42 andtiming pulses 44 are so timed as to produce three impulses 52 per field,each impulse preceding the data from the source with which it isassociated.

Other circuitry, not shown, produces the video information signals andthe synchronizing pulses (including the vertical synchronizing pulseswhich are produced by other circuitry) are combined with the video andtransmitted in conventional manner by closed circuit to the variousmonitors.

The transmitted signal is received at terminal 60 at each monitor andpasses through video amplifier 62. The video information signals passtherefrom through a normally open gate 92 and a video detector to thepicture tube for display. When the gate 92 is closed, it blocks signalflow and prevents display. The synchronization signals are separatedfrom the video in synchronization separator 64. The synchronizationsignals are then supplied to input 66 of gate 68, the input of avertical integrator and amplifier 70 and to input 76 of gate 78. Theoutput of gate 68 is connected via inverter 72 to the input of a singleshot multivibrator 74. The output of multivibrator 74 is connected toinput of gate 78 and is connected through inverter 82 to input 84 ofgate 68. The output of integrator 70 is connected to inputs 84 and 86 offlip-flops 88 and 90. The-output of gate 78 isconnected to input 102 ofOne or more of output terminals 104 and 106 of flip-flops 88 and 90 canbe connected directly or via logic to be described to electronic switch92. Switch 92 is connected to terminal 60 for selective groundingthereof as described below.

The horizontal synchronizing pulses with or without impulses 52, Le,pulses 48 or 54 are supplied to input 66 of gate 68. The output signal94 from inverter 82 is supplied to input 84 of gate 68. The outputsignal 96 from gate 68 is normally high. However, upon the arrival of apulse 48, signal 96 goes low. Signal 98 at the output of inverter 72goes high, triggering multivibrator 74 to produce a positive going pulse100 of positive polarity. This pulse, inverted by inverter 82 is appliedto gate 68 whereby signal 96 returns to its high state.

Pulses 100 and 48 are supplied to gate 78 which derives therefrom a highsignal 102.

Upon the arrival of a pulse 54, however, the presence of impulse 52therein varies the time of generation of the positive going pulse 100 atthe multivibrator, whereby the output signal 108 at gate 78 goes lowduring that portion of the period of pulse 54 which is in timecoincidence with the presence of the positive going pulse 100.

These low portions of signal 108 represent control impulses and are usedas described below to generate pulses for closing gate 92 to produce theselective blanking action at the face of the picture tube of the monitorunder consideration. To this end, signals 108 are supplied to the input102 of flip-flop 88. Flip-flops 88 and 90 constitute a two stage counterwhich is advanced one count whenever signal 108 goes low.

The vertical synchronizing pulses yielded at separator 64 are integratedand amplified to provide low going impulses l at the beginning of eachfield. These pulses are supplied to inputs 84 and 86 of flip-flops 88and 90 to reset both to their initial state. (This is necessary, sincethe counter can count to four, and there are only three blanking pulsesper field. Unless the counter is reset, the circuitry will functionimproperly).

The resulting signals at output terminals 104 and 106 are shown at 112and 114 respectively. Note that signal 112 is high during the New YorkExchange portion of the display and during the News Service portion ofthe display and is low at all other times, while the signal 114 is highduring the New York and American Exchange portions of the display and isotherwise low.

Thus, if signal 112 is supplied to gate 92, the gate would be closedduring the period when transactions of the New York Exchange are beingreported and when the News Service was to be displayed whereby only theAmerican Exchange transactions would be displayed. Similarly if signal 114 is supplied to gate 92 only the news would be displayed.

By gating these signals together in gate 116, signal 118 can beproduced. This signal can be inverted by inverter 120 to produce signal120 for supply to gate 92, thereby enabling display of the AmericanExchange transactions and the News Service while cutting off the displayof the New York Exchange transactions. Signal 118 can be supplieddirectly to the gate 92 to provide for the sole display of the New YorkExchange transactions. Signal 126 can be easily derived to provide forthe sole display of the American Exchange transactions.

Thus, depending upon the particular blanking conditions required, gate116 and inverter shown in box 128 may or may not be used and the circuitconnections shown in phantom can be varied as required.

The control impulses can be inserted in any synchronizing pulse,vertical or horizontal, and can be used at the monitor for purposesother than blanking, for example, sounding an alarm or flashing a lightfor special news announcements and the like.

While we described our invention with particular reference to preferredembodiments, our protection is to be limited only by the claims whichfollow.

What is claimed is:

1. A circuit comprising:

first means to produce a pulse train of regularly spaced pulses;

second means to produce control pulses at preselected time intervals,each such interval having at least a portion thereof in time coincidencewith a portion of the period in which a pulse is produced in said train;

timing pulse-generating means operative to generate an event pulsehaving a duration less. than the duration of a pulse from said pulsetrain and a pulse from said second means;

third means to produce an impulse whenever the condition of timecoincidence exists between the pulses from said first means, secondmeans and said timing pulse-generating means; and

fourth means to combine said pulse train with said impulses to produce acomposite pulse train.

2. A circuit as set forth in claim 1 further including fifth meansresponsive to said composite pulse train to detect the presence of saidimpulses in said composite train and to produce an additional controlpulse each time one of said impulses is detected.

3. A circuit as set forth in claim 2 wherein said pulse train containsonly rectangular pulses of one selected polarity.

4. A circuit as set forth in claim 3 wherein said impulses all have thesame polarity.

5. A circuit as set forth in claim 4 wherein said impulses aresuperimposed upon said rectangular pulses, the polarity of thesuperimposed impulses being opposite to that of said rectangular pulses.

6. A circuit as set forth in claim 5 wherein the additional controlpulses all have the same polarity.

1. A circuit comprising: first means to produce a pulse train of regularly spaced pulses; second means to produce control pulses at preselected time intervals, each such interval having at least a portion thereof in time coincidence with a portion of the period in which a pulse is produced in said train; timing pulse-generating means operative to generate an event pulse having a duration less than the duration of a pulse from said pulse train and a pulse from said second means; third means to produce an impulse whenever the condition of time coincidence exists between the pulses from said first means, second means and said timing pulse-generating means; and fourth means to combine said pulse train with said impulses to produce a composite pulse train.
 2. A circuit as set forth in claim 1 further including fifth means responsive to said composite pulse train to detect the presence of said impulses in said composite train and to produce an additional control pulse each time one of said impulses is detected.
 3. A circuit as set forth in claim 2 wherein said pulse train contains only rectangular pulses of one selected polarity.
 4. A circuit as set forth in claim 3 wherein said impulses all have the same polarity.
 5. A circuit as set forth in claim 4 wherein said impulses are superimposed upon said rectangular pulses, the polarity of the superimposed impulses being opposite to that of said rectangular pulses.
 6. A circuit as set forth in claim 5 wherein the additional control pulses all have the same polarity. 